Neuroanatomical, electrophysiological, functional imaging and lesion data indicate that the amygdala, hippocampus and orbital frontal cortex contribute to primate social and emotional behaviors. However, due primarily to past methodological deficiencies, the involvement and specific contributions of these brain regions in a circuit responsible for adaptive social behavior and emotional expression are still a matter for debate. The research program described in this proposal will rectify some of these deficiencies by combining ethologically-valid behavioral observations, semi-naturalistic testing environments and precise lesioning techniques to investigate two specific aims. First, the specific contributions of the amygdala, hippocampus and orbital frontal cortex to emotional reactivity in rhesus monkeys (Macaca mulatta) will be studied using three paradigms, each displaying a different visual stimulus in distinct environments. Second, the contributions of these neural regions to group social interactions will be studied in the same subjects. Social skills will be examined while four individuals interact in a large enclosure and social variables, such as group membership and size, will be systematically manipulated and controlled. The results generated from these two investigations will provide a new and sophisticated understanding of how the primate brain uses emotion to modulate social behavior adaptively.